$.getjson () Cross-domain request instance detailed

A common Getjson in jquery to invoke and get a remote JSON string, convert it to a JSON object, and execute the callback function if successful. The prototype is as follows:

Jquery.getjson (URL, [data], [callback]) loads JSON data across domains.

URL: Send the requested address
data: (optional) Key/value parameters to be sent
callback: (optional) callback function on successful load

Primarily used for client-side capture of server JSON data

1, the same domain name and other requests can be the same

Js:

The code is as follows	Copy Code
var url= "Http://localhost:2589/a.ashx"; $ (function () { $.getjson (url,function (data) { Alert (data. Name); }) });

Server return string:

The code is as follows	Copy Code
{' Name ': ' Loogn ', ' age ': 23}

2, under different domain names

Js:

The code is as follows	Copy Code
var url= "http://localhost:2589/a.ashx?callback="; $ (function () { $.getjson (url,function (data) { Alert (data. Name); }) });

Server return string:

The code is as follows	Copy Code
jquery1706543070425920333_1324445763158 ({"Name": "Loogn", "Age": 23})

The returned string is a function called "jquery1706543070425920333_1324445763158", and the argument is

The code is as follows	Copy Code
{' Name ': ' Loogn ', ' age ': 23}.

In fact, this very long function name is the role of callback= in the request path, I think it should be: The $.getjson method generates a reference to the callback method name, replace? The request above will become

http://localhost:2589/a.ashx?callback=jQuery1706543070425920333_1324445763158&_= 1324445763194, the server returns JSON to be processed, such as:

The code is as follows	Copy Code
String cb = Context. Request["Callback"]; Context. Response.Write (CB + "(" + JSON +) ");

Parameter name callback can also be replaced by Jsoncallback, I think is afraid of conflict, jsoncallback should be priority detection, no further detection callback (no test!!) )

？ is also a specific function name, so that the callback function can not be anonymous, with? The build is just a convenience that jquery provides for our general operations.

If it doesn't make sense, we'll look at one more example.

A.com uses $.getjson to send a request to the B.Com, and at the same time as the request, A.com puts the required delivery into the temporary file (or Membercache),

B.Com receives the request, in turn requests the required data to the A.com, carries out the necessary operation, then gives A.com returns the successful information. This achieves the goal of a cross-domain large volume of data request.

Of course, the communication process, preferably with the agreement, security.

JS Code:

The code is as follows	Copy Code
$.getjson (target_url+ "jsoncallback=?"), { ' userid ': <?php echo $userid;? > }, function (Result) { If (Result!= ' SC ') { alert (result); }else{ Top.document.getElementById ("menu"). src = $ (' #url_ ' +bid). Val () + "admin/left_menu.php"; Top.document.getElementById ("main"). src = $ (' #url_ ' +bid). Val () + "admin/index_body.php"; } });

PHP Server-side code:

The code is as follows	Copy Code
Header (' Content-encoding:plain '); $userid = SS ($_request[' userid ')); Logical code $msg = SC; $json _str = Json_encode (Array ($msg)); echo $_request[' Jsoncallback ']. ' (' $json _str. ') '; Exit Header (' Content-encoding:plain ');

This sentence is very important, if there is no such sentence, under IE6 will not be able to return information, resulting in the callback function can not be executed.

Also found on the internet, not verified

The code is as follows	Copy Code
<a href= "javascript:void (0);" ></a>

As a submit button will also cause IE6 under $.getjson error.

The submit button cannot be placed inside the <form> tag, otherwise the form interrupts the HTTP request issued by $.getjson.